Before jumping in and asking if I already Googled the topic, yes I have.
Furnace - 1990 Carrier 58GP-125-111DA, no run capacitor for the blower motor; yes this is a PSC motor and not an ECM.
Programmable thermostat kicks the burners on, however, when the temperature on the heat exchanger hits the threshold for the blower to kick on, there's a buzzing noise, the blower motor does not run/kick on (not without giving the blower cage a spin to overcome the initial inertia).
Oddly enough, the fan switch which is wired to "high" generally does turn over the blower motor and gets it to run. (ie. no buzzing).
Ended up taking out the blower motor assembly and found out it was an old GE Single Phase AC motor w/o the ability to add a run capacitor. I broke things apart and oiled the motor just in case. Reassembled and upon reconnecting everything, it spun over with the power turned on again. (direct fan switch)
Low and behold though, when the burners kicked on and try to turn on the blower motor, the same buzzing noise returned. I checked it wasn't a stuck relay on the control board, the buzzing was from the GE AC motor itself.
At this point in time, I'm not sure if it could be the selected speed for the thermostat triggered fan output is giving enough voltage (vs the highspeed setting) - which would mean a bad control board.
Or if it's just the GE AC motor getting long in the tooth and requires replacement.
Going to try changing the thermostat/temp triggered fan speed from low/med to med/high to see if that makes a difference.
Anyone have any ideas?